The invention relates to a rubber material of a wiper blade for windshield wipers, to a wiper blade comprising this material, and also to a process for production of this material.
Wiper-rubber materials for windshield wipers are subjected to a wide variety of physical and mechanical requirements. By way of example, they not only have to provide a satisfactory wiping result on, for example, a glass surface that requires cleaning, but also have to be abrasion-resistant and UV- or ozone-resistant.
By way of example, JP 358 758 7 B2 discloses wiper blades designed using a mixture of natural rubber and chloroprene together with fillers and processing aids. However, natural rubber and chloroprene have different polarities, natural rubber being relatively nonpolar, whereas chloroprene is polar.
This polarity difference between the two rubber components not only hinders the mixing of the two rubber materials for purposes of production of the wiper-rubber material but can also lead to migration, into the more polar chloroprene phase, of the processing aids such as vulcanization chemicals, e.g. accelerators or retarders, or of plasticizers and process auxiliaries. By way of example, the increased concentration of these substances in the chloroprene phase poses the risk of premature hardening in the crude rubber mixture, producing microscopic prevulcanizates which can markedly impair the wiping quality of a resultant rubber material. Another possible result of inhomogeneous distribution of the curing agent in a crude rubber mixture is local incomplete curing or local excessive hardening of the rubber system, and this can have a disadvantageous effect on the ageing properties of a resultant wiper rubber.